He said: "He's off to China again, but nothing has been mentioned at cabinet or any committee. I'm not against foreign visits, in fact I encourage them if they are good for the city.

"But we need to be able to assess what the tangible benefits to Birmingham are.

"When Labour led Birmingham City Council I took enough criticism for overseas visits, the Tories said they were a waste of time and money. But we were open about them."

The trip is Coun Whitby's third to China since he became council leader in 2004.

He will sign a Memorandum of Understanding with Nanjing, as the first step towards becoming a twin city.

He will also tour the Nanjing Automobile factory where he will discuss the future of the Longbridge factory.

And Coun Whitby's delegation is also guest at the Canal Cities Regeneration Forum in Yangzhou, where he will push the case for increased investment in Birmingham.

While the cost of staying at the forum is paid for by the hosts, Birmingham City Council is footing the rest of the bill for the tour.

Since becoming city leader Coun Whitby has made a concerted effort to forge ever closer links and secure business investment from China.

Last December Birmingham was twinned with the Chinese city of Guangzhou and in June the Chinese Ambassador to the UK, Madame Fu Ying, visited Birmingham to launch a new China-Birmingham Business Forum.

Coun Whitby said these relationships are bringing huge dividends for Birmingham.

"We have started working together in a range of areas such as environmental improvement, low carbon energy and the 2008 and 2012 Olympic Games," he said. OMy visit to China will move this agenda forward."